The present inventive concept relates to an analog-to-digital converters (ADC) and image sensors including ADC. More particularly, the inventive concept relates to ADC having reduced power consumption and image sensors including same.
Image sensors are devices that capture images as detected optical signals, and generate corresponding digital data using certain properties inherent in semiconductor materials. Recent developments enhancing the performance and reducing the cost of complementary metal-oxide-semiconductor (CMOS) technology have resulted in a widespread use of CMOS image sensors.
Many CMOS image sensors use correlated double sampling (CDS) to process digital data. That is, many CMOS image sensors essentially “count” a signal as it is sampled using CDS (e.g., a difference between a reset signal and an image signal is detected on a time-wise basis). The resulting count value is used to generate a digital signal. However, power is consumed during the counting function, and the extent of the counting function is proportional to a luminance component of the detected optical signal. Hence, higher luminance results in extended counting, which in turn results in relatively more power consumption. Accordingly, it is desirable to reduce, limit or minimize the extent of counting when relatively high luminance is apparent.